CET Semiconductor Devices & Circuits 2 — Questions and Answers
Question 1: What is the primary function of a Zener diode in a circuit?
- Amplify AC signals
- Regulate voltage by operating in reverse breakdown (Correct answer)
- Rectify AC to DC
- Store electrical charge
Correct answer: Regulate voltage by operating in reverse breakdown
A Zener diode is specifically designed to maintain a stable reference voltage when reverse biased at its breakdown voltage.
Question 2: In an NPN transistor, which terminal is the source of electrons during normal active-region operation?
- Collector
- Base
- Emitter (Correct answer)
- Substrate
Correct answer: Emitter
In an NPN transistor, the emitter injects (emits) electrons into the base region during forward-active operation.
Question 3: A silicon diode has a forward voltage drop of approximately:
- 0.1 V
- 0.3 V
- 0.7 V (Correct answer)
- 1.4 V
Correct answer: 0.7 V
Silicon diodes have a characteristic forward voltage drop (barrier potential) of approximately 0.6–0.7 V.
Question 4: What does the parameter hFE (or β) represent for a BJT transistor?
- Cutoff frequency
- DC current gain (IC/IB) (Correct answer)
- Transconductance in siemens
- Reverse saturation current
Correct answer: DC current gain (IC/IB)
hFE (β) is the DC current gain, defined as the ratio of collector current to base current in a BJT.
Question 5: Which biasing configuration for a BJT provides the most stable Q-point against temperature variations?
- Fixed bias
- Collector-to-base bias
- Voltage-divider bias (Correct answer)
- Emitter bias with dual supply
Correct answer: Voltage-divider bias
Voltage-divider bias sets the base voltage independently of β, making the Q-point very stable over temperature and device variation.
Question 6: In a MOSFET, the channel conductivity is controlled by the voltage applied to which terminal?
- Drain
- Source
- Gate (Correct answer)
- Body
Correct answer: Gate
The gate voltage creates or modulates the inversion channel between source and drain, controlling drain current.
Question 7: A full-wave bridge rectifier uses how many diodes?
- 1
- 2
- 4 (Correct answer)
- 6
Correct answer: 4
A full-wave bridge rectifier uses four diodes arranged so both half-cycles of the AC input produce positive output.
CET Semiconductor Devices & Circuits 2
What is the primary function of a Zener diode in a circuit?